Devices for cutting and sealing cut edges of thermoplastic materials have been known for some time. Refer, for example, to U.S. Pat. No. 4,534,819 to Payet and Ballard for an apparatus and process for cutting and sealing a woven textile fabric having thermoplastic fibers to prevent the fabric from raveling after repeated washings. Disclosed are an anvil in the form of a roller having a doubly beveled peripheral surface, an ultrasonic cutting and sealing device, and material feeding means. Also disclosed are material feeding speed, anvil angle, cutting device frequency and anvil-cutting device spacing. U.S. Pat. No. 4,693,771, also to Payet and Ballard, discloses a similar apparatus and process.
U.S. Pat. No. 4,496,407 to Lowery and Payet discloses an apparatus and process for ultrasonically cutting off undesirable selvage and sealing the edge using a stationary cutter while moving the fabric for processing one edge and using a laterally movable cutter while moving the fabric for simultaneously processing an opposite edge. Also disclosed are a hydraulic fabric shifter and process and position sensors.
Another apparatus for ultrasonically cutting and sealing sheet workpieces together is disclosed in U.S. Pat. No. 3,657,033 to Sager. This apparatus includes an anvil having an inclined surface and a blade having a radius contacting edge. When ultrasonically vibrated, the blade applies a component of force acting perpendicularly to the contacting edge of the blade and a component of force acting parallel to the inclined surface of the anvil to simultaneously seal and cut material as it moves along between the blade and the anvil. The blade and anvil may also be moved relative to the material.
U.S. Pat. No. 3,457,132 to Tuma and Gafvert disclose an apparatus for cutting and heat sealing two webs of material together using a heated member, which may be ultrasonically heated, having different surface temperatures at different areas of its surface, a hot central area being used to cut material and lateral areas of lower temperatures to heat and seal together sheet material pressed thereby.
U.S. Pat. No. 4,157,719 to DeWoskin discloses an apparatus including shaped cutting edges that cut material adjacent that portion thereof being sealed by an ultrasonic horn acting against an anvil. The cut material is blown away.
Several devices introduce a separate, thermoplastic thread to cutting and sealing areas to facilitate the sealing of nonthermoplastic materials. For example, U.S. Pat. No. 4,560,427 to Flood discloses an ultrasonic sealing and cutting method and apparatus having a roller-shaped anvil. The anvil has a doubly beveled peripheral surface forming a centrally disposed cutting edge. A thermoplastic thread is fed through a cutting station with the fabric, proximate one beveled surface of the anvil, to be fused with the fabric. This allows low-thermoplastic-content material to be sealed.
Another example of the use of thermoplastic thread is U.S. Pat. No. 4,610,750 to Mango, which discloses an ultrasonic cut and seal apparatus having a roller-shaped anvil. The apparatus includes a cutter having a removable tip the longitudinal axis of which is offset somewhat from the axis of rotation of the roller. The tip defines therein an inclined bore through which a thermoplastic filament is fed to be fused with sheet material being cut and sealed.
U.S. Pat. No. 4,224,091 to Sager discloses a method for producing a corner in thermoplastic material using ultrasonically cutting and sealing.
U.S. Pat. No. 4,491,491 discloses an ultrasonic separation apparatus for simultaneously cutting and sealing thermoplastic material. Included is a resilient cutter mounting. The apparatus may be particularly adapted to cut strings of pocketed coil springs.
While each of these cutters and sealers functions with a certain degree of efficiency, none disclose the advantages of the improved ultrasonic cutting and sealing system of the present invention as is hereinafter more fully described.